In preparation for becoming an internal plugin in chrome I did these things:...

plugin/cross/config.h

 /*
  * Copyright 2009, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 22 matching lines @@
 // This file defines a few functions to check the user's hardware and software
 // configuration.
 
 #ifndef O3D_PLUGIN_CROSS_CONFIG_H_
 #define O3D_PLUGIN_CROSS_CONFIG_H_
 
 #include <fstream>
 #include <string>
 #include "plugin/cross/o3d_glue.h"
 
+namespace o3d {
+
 // Returns the user agent string.
 // Arguments:
 //   npp: plugin instance.
 // Returns:
 //   The user agent string.
 std::string GetUserAgent(NPP npp);
 
 struct GPUDevice {
   unsigned int vendor_id;
   unsigned int device_id;
@@ skipping 52 matching lines @@
 // into metrics.
 bool GetUserConfigMetrics();
 
 // Checks the browser version.
 // Arguments:
 //   npp: plugin instance.
 bool GetUserAgentMetrics(NPP npp);
 
 bool GetOpenGLMetrics();
 
+}  // namespace o3d
+
 #endif  // O3D_PLUGIN_CROSS_CONFIG_H_